A general receiver adopting a super-heterodyne method converts a frequency by using a mixing circuit after amplifying a modulated wave signal received via an antenna at a high frequency, and demodulates it after converting it into an intermediate-frequency signal having a predetermined frequency.
Particularly, in recent years, a research is underway as to a technology for integrally forming an analog circuit including a high-frequency component on a semiconductor substrate by using CMOS process or MOS process, which is put to practical use in certain apparatuses. It is possible, by forming various kinds of circuits on one chip by using the CMOS process or the MOS process, to miniaturize and reduce cost of the entire apparatus. Therefore, it is thinkable that the range of the apparatuses to be formed on one chip will expand from now on.
To form the components of a receiver in the past adopting a super-heterodyne method on one chip by using the CMOS process or the MOS process, there is a problem that low-frequency noise called 1/f noise increases. In general, compared to a bipolar transistor, a MOS-type FET is characterized by having high 1/f noise. And if the components constituting the receiver are formed on one chip by using the CMOS process or the MOS process, an FET as an amplification element included therein becomes a source of the 1/f noise. Moreover, in the case of converting a modulated wave signal of a high frequency into an intermediate-frequency signal of a low frequency by using a mixing circuit, a ratio of the 1/f noise component in the intermediate-frequency signal becomes higher, resulting in deterioration of receiving quality due to decline in an SN ratio.